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Discussion Starter #1
I hit 200k on my 2007 Sienna Limited FWD last fall. Shortly after that, I had the “Check Engine” light come on, almost immediately followed by VSC and TRAC OFF. The same lights came on around 160k; that ended up being a leaky gas cap. So when it happened again at 201k, of course I replaced that first (after checking/tightening didn’t do anything), but that “cheap” option didn’t do anything this time.

Finally took it in for diagnosis late Nov. 2019, error code came back with faulty #5 ignition coil. Replaced that and everything was fine...for 2 months. Same thing happened around Feb 5th, this time getting faulty #4 ignition coil, which I also replaced. Lights came back on today. I’m assuming when I go in, they’re going to tell me that yet another ignition coil is faulty.

I am aware that being over 200k, I can expect things to begin failing, but is it normal for these ignition coils to fail one at a time, yet so quickly one after another? I’m beginning to feel a little paranoid that maybe the Toyota place is doing some pre-emptive sabotage.?..

So, assuming I’m just paranoid and it is actually normal, would it make more sense to have them replace all remaining ignition coils when I go in this time, instead of doing this piecemeal crap? If nothing else, I’m sick of paying $70 every time I go in just to be told what is wrong (and the part that really sucks is that is the cheapest diagnostic fee at any Toyota service department in my area!). And I assume that the overall labor cost would be less if I just had them all done in one swoop instead of one at a time?

The other question would be, is the Toyota service dept. failing to let me know about some potential “upline” fault that could be the reason that the ignition coils continue to go bad, and if I could just fix “that thing” would it insure against the coils continuing to go out? If so, any idea what that thing might be?

Thanks for any input!
 

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For 200k miles, that's impressive and you can expect them to fail at this mileage. I guess when it rains it pours! If I were you I would just replace the other ones that haven't failed as preventive maintenance. Or wait until another fails and replace all the old ones. Coil #1,3, and 5 are the hardest to replace since they are in the back. Also replace all the spark plugs too.

I replaced all the spark plugs myself on my 2007 Sienna at 118k on 6/15. Then coil #6 went bad at 151k on 2/18. Coil #2 recently at 177k on 1/20. All were original coils. I've been lucky all the bad coils have been the easy ones in front because the back ones are a pain. If any one of the back ones goes, I will replace all coils and spark plugs. I put up a diagram of the coil locations below for reference.

45602
 

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I am surprised to hear of so many coil failures if the spark plugs have been replaced on schedule. The usual cause of coil failure is when spark plugs go well beyond their recommended interval and their gaps are too large, meaning too much power is drawn through the coil to create a spark. It’s a classic example of an ounce of prevention is worth a pound of cure. Replace those sparkers on time and you shouldn’t have any coil problems.

If you’ve replaced your plugs at 120k like Toyota recommends I think it’s strange that you’re experiencing all these coil failures. For reference, I have an 06 with 181k, all on the original spark plugs (shame on me, will replace soon) and original coils.

If you’re still on your original plugs for heavens sake change them out. And yeah since cylinders 1, 3 and 5 are so darn hard to access, put new coils in for 1 and 3 while you’re at it.
 

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Discussion Starter #4
We started with this vehicle at its 90k, and I did the spark plugs at 120k as Toyota recommends.

After all my hand-wringing, my problem turned out NOT to be another ignition coil. It was the oxygen sensor. Followed by the fuel-air sensor 4 days later. [sigh, groan, huff, scream, empty paycheck directly into mechanic’s pocket] Those were my primary suspects the first two times that turned out to be ignition coils.

I hit 210k today, so I’m definitely open to suggestions for cheaper preventative maintenance efforts that will head off more expensive repairs. Logic would say spark plugs again at 240k, but maybe a higher-mileage vehicle means a shorter life-span? Any idea on whether the remaining old ignition coils ought to hold out? (Pricing things out after already having done two, I’ve concluded I could’ve done all six at once for approximately 40% of what it’ll cost me in parts and labor doing them one at a time.)
 

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Get a code reader or take the van to an autoparts store to have the code(s) read before you take it to the mechanic. That will take some of the mystery out of owning and maintaining a high-mileage vehicle.
 

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I still feel surprised you had two coils go bad after replacing spark plugs at the recommended interval. We’re they oem or equivalent replacements?
I would only do the spark plugs again at 240 if you are definitely going for a high ultimate mileage like 280-300k total or beyond. I think there’s plenty of give in the recommended schedule (but I know I’m pushing it with my plugs at 180k)
 
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